JPS6146283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a dry fiber board, and more particularly to a method for forming a black rock-like layer formed during thermo-pressure molding of the board uniformly and flatly on the surface of the board.

To manufacture fiberboard using the dry method, each fiber is first defibrated, an adhesive is added, and then classified, and then each fiber is deposited on a screen belt to a certain thickness, pre-pressed, and then cut using a cross-cutting machine. After that, it is hot-pressed and molded using a hot press.
However, during this hot-pressing process, the surface fibers of the fiber mat that are in contact with the hot plate of the hot press are rapidly heated, and the moist moisture moves into the mat as steam before sufficient heat-pressing, and the mat surface Despite the adhesive being attached to the fibers, the moisture content is low and insufficient adhesion occurs, resulting in the formation of a low density, poorly bonded, and weak layer.
A layer with high strength called a black bedrock layer is formed under this low-strength surface layer. Therefore, such fiberboards are easily damaged even when used as is, and are easy to peel off even when painted or attached with other materials, and have low commercial value. Under these circumstances, this low-strength layer is currently removed by sanding to improve secondary processability and enhance product quality. This sanding removes a thickness of 1 mm or more, and since it involves grinding something that has been formed flat, it significantly reduces the workability of fiberboard manufacturing and also reduces the yield. It is also decreasing.

For this reason, if this black rock-like layer is formed on the surface of the board during hot pressing using a hot press, not only will grinding work become unnecessary, but
The surface strength is further improved, and it has extremely high industrial significance in the production of dry fiberboard.

Conventionally, from this viewpoint, various proposals have been made to form a black rock-like layer on the surface of the fiberboard during thermo-pressure molding. For example, there was a concept of sprinkling water on the pine surface after forming the fiber pine and before hot pressing to make the surface of the pine high in moisture content during hot-press molding, but it is necessary to spray water so that the pine surface has a high moisture content evenly. If this is not done, a black rock-like layer will partially form near the surface, and so-called moisture spots will be formed, impairing the surface quality.Also, if the amount of water sprayed is too large in some areas, water vapor will be generated during hot-pressing or depressurization. In addition, many problems occurred, such as fiber lumps adhering to the press belt during pre-pressing or similar adhesion to the press plate of the hot press. Since these drawbacks exist in the surface watering method, water is sprinkled on the surface of the fiber mat,
In addition, it has been proposed to sprinkle on the surface of the fiber mat temporarily coated fibers that are not adhesive-containing and are made water-repellent by wax, which is not useful for forming fiberboards. In this case, if the temporarily coated fiber is removed after hot-pressing molding, a black rock-like layer will be formed on almost the surface of the original mat for forming the fiberboard, and the coated fiber layer formed on the fiberboard will contain adhesive. It was said that it could be easily removed with a sander because it was not present (Special Publication No. 51-29753). However, although this method was able to prevent fiber lumps from adhering to the belt or press plate during pine transportation or hot-pressure molding, it was not able to sufficiently prevent the formation of moisture spots and rupture. , and did not completely solve the problem.

An object of the present invention is to provide a method that solves the problems of the conventional method and makes it possible to more stably manufacture a fiberboard having a black rock-like layer on the surface.

That is, the present invention involves placing water-impregnated nonwoven fabric, paper, cloth, or other water-retentive sheet material on a fiber mat before hot-pressing molding in the production of dry fiberboard. Preferably, after pre-pressing and cross-cutting, the sheet-like material is placed, wetted with water by spraying water, etc., and then hot-press molded to form a black rock-like layer on the surface of the fiberboard. This is a method of forming.

This will be explained below according to the illustrated embodiment.

Referring to FIG. 1, a forming device 1 is used in an ordinary dry fiberboard device, and the fibers of each layer to be formed after being defibrated and resin are added are sequentially conveyed to a screen conveyor 2. The fiber mat A is formed by depositing the fibers on top and adjusting the thickness of each layer using the shaping rotor 3. Fiber mat A
is temporarily pressed by the prepress device 4. The pre-pressed fiber mat A is cut into a predetermined length by the cross-cutting device 6 while being conveyed by the conveyor 5, a gap is formed between the standard length mats A' and A', and the ears of the mat are removed. . Next, before this mat A' is inserted into a hot press, the thin paper 7 covering the entire surface of the mat A' is rolled and twisted by a winding device 8.
The material is rolled and twisted and cut using the cutting device 9 between the fixed length mats A' and A'. After that,
Water is sprayed or applied onto the tissue paper 7 placed on the mat by a water supply device 10, which may be a sprayer, a flow coater, or the like.

The pretreated standard mat A' is placed on a call plate 11 as usual, inserted into a hot press 12, and heated and pressed to form a board. However, the fixed length mat A' inserted into the hot press 12 is not directly sprayed with water on the fiber mat as in the conventional method, but has a substantially uniform density like the thin paper 7, which has a higher density than the fiber mat. Since the water is sprinkled on a tall sheet, the sprinkled water is uniformly contained over the entire surface of the sheet.
Therefore, when the hot plate of the hot press 12 comes into contact with the mat, the moisture in the tissue paper turns into steam and transfers into the mat, but since the tissue paper has a high water retention capacity, the amount of residual moisture is large and causes a black rock-like appearance on the mat surface. It is possible to form layers well.

The board that has been hot-press molded with the thin paper 7 placed on its surface is then subjected to a brush roll or sander to remove the thin paper on the surface, but it remains as a protective layer until secondary processing, and is removed immediately before processing. It's okay if it gets lost.

In this way, in the conventional method, water is directly sprinkled on the low-density fiber pine, so even if the water is sprinkled uniformly, the penetration into the pine is concentrated in one part depending on the state of fiber accumulation in the pine, resulting in uneven moisture distribution. In contrast, in the present invention, the thin paper covered on the mat has a relatively high density and uniformity, and has good water permeability and water retention, so the sprayed water is uniformly stored on the mat. Moisture spots caused by locally high moisture content do not form, and surface properties do not deteriorate. Of course, this also prevents the tube from bursting due to excessive moisture.

Further, in the above embodiment, water is sprinkled or applied after the dry sheet of tissue paper is placed on the mat, but water may be already impregnated before the sheet is placed on the mat. Further, the sheet may be turned over at any position before hot-pressing molding, and at a position compatible with the mat molding line. In this way, in the present invention, since the sheet is already overturned at the time of watering, there is no possibility that part of the fiber mat will adhere to the belt or roller of the prepress, the hot plate of the hot press, etc.

Examples are shown below.

Example (manufacture of 7 mm thick board) Fibers that have been defibrated in advance and mixed with adhesives and water repellents and have a water content of 8 to 15% are blown into a forming device at a conveying speed of 10 to 15 m/min. Each fiber is sorted on a moving wire mesh conveyor, and the thickness is adjusted using a sheave rotor, and the fibers are formed one by one.
A fiber mat with a thickness of 100 to 110 mm was formed.

This mat was continuously pressed using a pre-press machine to obtain a pre-tight mat with a thickness of 40 to 50 mm.

The temporary mat was cut to a specified length using a cross cut saw, and the ears were also removed. A strip of continuous thin paper weighing 20 to 50 g/m ² was placed on top of this, and then the thin paper was cut to a length slightly longer than the mat length using a clipper.

Water was uniformly sprayed onto the pine on which the tissue paper was placed, so that the tissue paper was impregnated with 30 to 40 g/m ² of water.

The pretreated mats of fixed length are sequentially inserted into each stage of the hot press, and the primary pressing is performed at a hot plate temperature of 180 to 230°C, 60 to 80 kg/m ² , and the total press time is 3 to 5 minutes.
It was pressed and plated under the following conditions.

After pressing, the board was conveyed to a subsequent process with or without humidity conditioning, and the thin paper was removed using a brush roll.

The fiberboard thus obtained has an extremely smooth surface, a thickness of 6 to 7.5 mm, and a specific gravity of 0.9 to 1.
and its surface strength was determined using a taper abrasion tester.
When the amount of wear was measured after 200 rotations, it was found to be 0.4 to 0.5 g, and it was found that an excellent black rock-like layer had been formed on the surface.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of an embodiment of the manufacturing method of the present invention, and FIG. 2 is a partial end view of a fiber board obtained by the method of the present invention. Description of symbols, 1: Forming device, 2: Wire mesh conveyor, 3: Shave rotor, 4: Prepress device, 5: Conveyor conveyor, 6: Cross cutting machine, 7: Thin paper, 8: Winding device, 9: Cutting device, 10: Water supply machine, 11: Coal plate, 12: Hot press, A: Black rock-like layer on the front surface, B: Black rock-like layer on the back surface, C: Back surface layer with low strength.

Claims (1)

[Claims] 1. A sheet-like material such as water-impregnated nonwoven fabric, paper, cloth, etc. is placed on the surface of a fiber mat before hot-pressure molding in the production of ordinary dry fiberboard, and the above-mentioned A dry process in which a black rock-like layer is formed on the surface of the fiberboard obtained from the fiber mat by hot-pressing molding, and further, after the hot-pressing molding, the sheet-like material is removed to expose the black rock-like layer. Method of manufacturing fiberboard. 2. The water-impregnated sheet material placed on the surface of the fiber mat before hot-press molding is placed on the pre-pressed fiber mat cut into a fixed length, and then The method for manufacturing a dry fiberboard according to claim 1, wherein the sheet-like material is then impregnated with water using a water supply machine. 3. The dry fiberboard manufacturing method according to claim 1, wherein the sheet-like material remaining on the fiberboard after the hot-press molding is not removed until the fiberboard is used.